Allergic Chronic Cough. Times a day?

Hi..I have chronic cough for last 12 years. It stays for about 3-4 months and is quite severe. I suffer from this cough each year. Doctors diagnose it as Bronchitis cough, CVA, allergy etc. All investaigation reports have always been clear. Medicines do not work and ultimately, doctors resort to steroids.One doctor prescribed me Gabapentin NT 400 at night but unfortunately it did not work even 1% and I kept coughing all night. My cough gets litter better upon head massage or when I am distracted. No cough when I am sleeping. Any advise? Recently, I read about Gabapentin being a good medicine for chronic cough. I nightstarting taking 300 mg three times a day and I see about 40-50% relief. Now, my question is - can I try and take 600 mg three times a day? The studies I have read says 1800 mg is well tolerated and is effective for people suffering from Chronic cough.